Background: Antiphospholipid syndrome (APS) is a thrombo-inflammatory disorder associated with significant morbidity and mortality. In the diagnosis of APS, lupus anticoagulant (LA) testing plays a crucial role. This testing involves assessing the presence of LA using a correction ratio calculated from the dilute Russell's Viper venom Time (dRVVT), a functional assay. Additionally, other antiphospholipid antibodies, such as anti-cardiolipin and anti-beta-2 glycoprotein I, have demonstrated a positive correlation between their titers and thrombotic events.

Aim: This study aims to evaluate the hypothesis that the correction ratio derived from dRVVT can predict the risk of thrombosis in patients who have tested positive for LA on more than one occasion.

Patients and methods: We conducted a single center retrospective cohort study, focusing on patients who are repeatedly tested positive for LA between September 2020 and June 2023. A total of 167 patients were included in the analysis. The mean age of the cohort was 50.4 years (±16.8), with 43.7% male and 56.3% female. We calculated both the highest and mean dRVVT correction ratios. Logistic regression was employed, with thrombosis as the dependent variable. Additionally, we performed a receiver operating characteristic (ROC) analysis to assess the predictive quality of the proposed model. Finally, we stratified the population into quartiles to illustrate the escalating risk of thrombosis at higher correction ratio quartiles.

Results: Among the 167 patients, 63 (37.7%) developed thrombosis. After adjusting for confounding factors, the odds ratio for thrombosis occurrence is 40.9 (95% CI [10.6-157.7], p < 0.01) per 1-unit increase in the highest dRVVT correction time. Similarly, the odds ratio for thrombosis occurrence is 72.2 (95% CI [14.2-367.8], p < 0.01) per 1-unit increase in the mean correction ratio. Additionally, a Pearson's correlation test revealed that the highest dRVVT correlates with activated partial thromboplastin time (APTT). Using the same logistic regression model, the odds ratio for thrombosis occurrence is 1.052 (95% CI [1.023-1.081], p < 0.01) per 1-unit increase in APTT when adjusted for covariates. Furthermore, ROC-AUC analysis demonstrated an area under the curve (AUC) of 0.805 (95% CI [0.735-0.874]). Quartile analysis revealed that the odds ratio for developing thrombosis in the 4th quartile, compared to the 1st quartile, is 30.5 (95% CI [9.8-113.9], p < 0.01).

Conclusion: The correction ratio derived from the dRVVT test positively correlates with thrombotic events. Our data suggest that dRVVT should be further studied as a predictive model for thrombosis.

Disclosures

No relevant conflicts of interest to declare.

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2024
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